Surface tension valves for microfluidic applications

Abstract

A passive valve for use within microfluidic structures. Surface tension forces developed within microscale channels are used to control flow within the channels. Flow can be halted within a channel until fluid force reaches a predetermined pressure to allow the channel to open.

What is claimed is:  
     
         1 . A microfluidic device, comprising: 
 a microfluidic channel having an inlet and an outlet;    a fluid flowing within said channel;    and a region within said channel between said inlet and said outlet containing material which causes increased surface tension in said fluid at said region,    such that fluid flowing into said inlet requires a fluid driving force greater to cross said region than that required to flow from said inlet to said region.    
     
     
         2 . The device of  claim 1 , wherein said material causing increased surface tension comprises a hydrophobic coating.  
     
     
         3 . The device of  claim 1 , wherein said material comprises a reduced cross-sectional area within said microfluidic channel.  
     
     
         4 . The device of  claim 1 , wherein said region is located adjacent said outlet of said microfluidic channel.  
     
     
         5 . The device of  claim 1  further comprising a second region within said channel between said first region and said outlet containing a second material which causes a greater increase in surface tension in said fluid at said second region.  
     
     
         6 . A passive valve for use in a microfluidic system, comprising: 
 a microfluidic first channel having a first inlet and a first outlet;    a second channel having a second inlet intersecting said first channel between said first inlet and said first outlet;    a first region located at the intersection of said second inlet and said first channel, having increased surface tension at said first region;    a first fluid flowing within said second channel having a fluid driving force which cannot overcome the surface tension at said first region, and thereby halting flow within said second channel;    and a second fluid flowing within said first channel and contacting said intersection,    such that said second fluid contacts said stopped fluid at said first region, and allows said first fluid to overcome the surface tension at said first region, and causes first and second fluids to flow within said first channel to said outlet.    
     
     
         7 . The valve of  claim 6 , wherein said first region contains a hydrophobic coating.  
     
     
         8 . The valve of  claim 6 , wherein said first region contains a hydrophilic coating.  
     
     
         9 . The valve of  claim 6 , wherein said first channel is constructed from a hydrophobic material.  
     
     
         10 . The valve of  claim 6 , wherein said second channel is constructed from a hydrophobic material.